Millimeter waves sensing behind walls - Feseability study with FEL radiation

Design of through-wall imaging (TWI) system needs the knowledge of constitutive parameters of different building materials. The paper describes the results of measurements of the effective attenuation constant of typical building materials such as concrete bricks, wood, tiles, sand, gypsum, etc. on mm-waves using powerful pulse FEL radiation. Since the Rayleigh criterion for surface roughness cannot be satisfied for majority of measured building materials on mm waves, the increased measured attenuation in comparison with bulky material is taken place. Additional experiments were performed to estimate a role of these effects using quasi-noise mm-wave source and wide-band mm-wave receiver.